Membranes & Integumentary System (p. 81- 107) Chapter 3 Membranes & Integumentary System (p. 81- 107)

Skin Our skin is an organ It makes up about 15% of your total body weight Considered the “Integumentary System” because it… Contains glands and sensory receptors Grows hair and nails

Membranes Surround and help protect the body’s surfaces 2 Categories 1. Epithelial membranes 2. Connective Tissue membranes

Epithelial Membranes Provide a lining for internal and external surfaces of the body Epithelial membranes are composed of… Sheet of epithelial cells Underlying layer of connective tissue

Epithelial Membranes There are 3 types of epithelial membranes 1. Mucous Membranes 2. Serous Membranes 3. Cutaneous Membranes

Mucous Membranes Mucous: slippery solution that protects mucous membranes and aids in transporting substances Line body cavities that open to the outside world Respiratory tract (nose, lungs) Digestive tract (mouth, stomach) Urinary tract (bladder) Reproductive tract

Serous Membranes Serous fluid: a thin, clear fluid that serves as a lubricant between the parietal and visceral membranes to minimize friction and “wear and tear” on organs Line body cavities that are closed to the outside world Pleura (around the lungs) Pericardium (around the heart) Peritoneum (around the abdominal cavity)

Cutaneous Membrane What we know as “skin” Keratinizing stratified squamous epithelium Underlying dense fibrous connective tissue Dry membrane when sweat is not present Contain sweat glands

Connective Tissue Membranes The only membrane only made up of connective tissue Include no epithelial cells Only one type: Synovial membranes Line capsules that surround synovial joints (shoulders and knees) Serve as cushions for tendons and ligaments surrounding joints Synovial fluid: clear fluid which provides cushioning and reduces friction and wear on moving structures

Functions of the Integumentary System 1. Protection First line of defense Outermost layer of skin contains keratin Tough protein also in hair and nails

Functions of Integumentary System 2. Water Barrier Keratin and natural skin oils serve as a water barrier Lessens evaporation of water Prevents water entering body while swimming or bathing

Functions of Integumentary System 3. Temperature Regulation Sweat glands and capillaries lie close to surface of the skin Body is hot  capillaries dilate  allows heat to leave Sweat glands activate, sweat evaporates, skin cools Body is cold  capillaries constrict  blood flow moves toward core of body to minimize heat loss

Functions of Integumentary System 4. Vitamin D Production Melanocytes: specialized cells in the skin that produce melanin Melanin: pigment that protects the body against harmful UV rays UVB rays convert modified cholesterol molecules into vitamin D Vitamin D: essential for bone health

Functions of Integumentary System 5. Waste Elimination Sweating eliminates chemical waste products from the body Urea, uric acid, salts **Sweat is acidic and helps protect the body against bacterial infections!**

Functions of Integumentary System 6. Sensory Perception Cutaneous sensory receptors are part of the nervous system Transmit nerve signals from the skin to the central nervous system Touch, pressure, vibration, pain, temperature